1. Field of the Invention
This invention relates to a novel derivative compound of 1,3- or 1,4-bis(hexafluoroisopropyl) benzene, or 2,2-bisphenylhexafluoropropane to be used for ink-repellent treatment, an ink-repellent agent containing such compound, a head ink jet recording coated on ink eject opening end surface with such ink-repellent agent, and an ink jet recording device equipped with such head.
2. Related Background Art
With propagation of computers in recent years, various application instruments have been actively developed. Particularly, remarkable progress can be seen in developement and propagation of office instruments for office automation such as copying machines, facsimiles, word processers and other so called personal computers, etc.
In these office instruments, the so called printer as the instrument for output of the processed data or sentences, etc. is an essential device.
In the prior art, as such printer, there have been employed a printer of the impact system such as wire dot printer, etc., a laser beam printer by use of the electrostatic copying system, a printer of the non-impact system such as heat transfer printer, etc., but a printer of the ink jet recording system is attracting attention in recent years because of its excellent characteristics, and developements of various systems are now under progress.
It is of course desirable that printing and images by a printer should be beautiful and precise, and the target of these printer techniques resides here. As a means for that purpose, one may consider to make ink eject nozzles smaller and arrange them closely to each other. For that purpose, there has been known the method in which a large number of eject openings are prepared closely to each other by use of the fine working system using the so called microlithographic technique.
FIG. 7 shows a constitutional example of an ink jet recording head of the prior art prepared according to such method. In FIG. 7, 71 is a first substrate formed of, for example, a silicon wafer, etc., 72 a layer formed of, for example. SiO.sub.2, etc. on the surface of the first substrate 1. 73 is a nozzle wall formed by such method as lithography, etc., 74 a second substrate formed of, for example, a glass plate, 75 an adhesive layer for adhering the second substrate 74 to the upper part of the nozzle wall 73, and 76 an ink eject opening of nozzle. Such recording is worked very precisely with the nozzle wall 73 being made to have dimensions of 25 .mu.m of height and 20 .mu.m of width, and the ink jet eject opening 76 to have the same dimensions as the nozzle wall 73.
FIGS. 8A and 8B show side sectional views of the ink jet recording head shown in FIG. 7, showing two examples under the state of forming ink droplets 88 by ejecting of the ink 87. FIG. 8A shows the state in which ink droplets are ejected straightforward without wetting of the eject opening end surface 89 with ink, while FIG. 8B shows the state in which ink droplets are going to be ejected slant, because a part of the eject opening end surface 89 is wetted with ink before ejecting.
The ejecting opening end surface 89 may be wetted and spread with ink during ink ejecting, or otherwise sometimes in a device in the form of performing recording with the recording head mounted on a carriage, the ink 87 within the nozzle may be overflowed outside from the eject opening end surface 89 to wet that portion by mechanical vibrations, caused by mechanical movement of the head when it performs printing, or when it returns again to home position after reaching of the carriage to the end of the recording medium.
Thus, when the ink overflowed to wet the eject opening end surface 89 is returned again within the eject opening, or when the peripheral portion of the eject opening is uniformly wetted, the eject direction of the ink droplets 88 becomes straight as shown in FIG. 8A, whereby the ejecting state, namely the recording state is stabilized.
However, in the ink jet recording head of the prior art, due to differences in wettability between the second substrate 74 and the adhesive layer 75, the eject opening end surface 89 may be wetted nonuniformly, or as shown in FIG. 8, nonuniform residual state of ink occurs on the eject opening end surface 89 after once wetted, whereby unstable ejecting state as shown in FIG. 8B occurs.
Thus, there is a strong relationship between wetting of the eject opening end surface and the surface state of the end surface, and when the surface state of the eject opening end surface is not adequate, an unstable ejecting state occurs, whereby a good recording state cannot be maintained, lowering the recording quality.
This is also a problem which occurs as a matter of course not only in the ink jet recording head of the constitution shown in FIG. 7 but also generally in an ink jet recording head which has an ink ejecting nozzle formed smaller and is adapted to perform ink ejecting at high velocity and high frequency. However, particularly in the case as in the ink jet recording head shown in FIG. 7, when ink eject openings are provided closely to each other, since wetting occurs around the eject openings adjacent to each other, wetting is connecting mutually between the adjacent eject openings, and its influences become increasingly greater. As the result, further remarkable adverse influences such as deformation of recorded letters or disturbance of the images may be exerted on recording quality or images, and therefore it is necessary to manage the eject opening end surface more strictly.
In the prior art, for the purpose of maintaining ink ejecting stability of an ink jet recording head, there have been made various proposals of performing an ink repellent treatment which is the surface treatment of the head surface.
As an example, as disclosed in Japanese Patent Laid-open No. 63-122560, there have been proposed the method in which removeable solids are filled internally of the eject opening to form a thin layer of an ink-repellent agent on the surface of an elastic member, and the thin layer is transferred onto the surface at the peripheral portion of the eject opening of the recording head, or as desclosed in Japanese Patent Laid-open No. 63-122557, the method in which while a gas is jetted out through eject openings, the recording head end surface having said eject openings is dipped in an ink-repellent agent.
Among such proposals, for enhancing the effect of the ink repellent treatment used, there has been frequently used a substance having many fluorine atoms (see Japanese Patent Laid-open Nos. 63-122550, 63-122557, 63-122559, 63-122560, etc.).
For example, as the treating agent which makes the eject opening end surface liquid-repellent, Japanese Patent Laid-open No. 56-89569 discloses use of undecafluoropentyltrimethoxysilane, tridecafluorohexyltrimethoxysilane, perfluorodecyltrimethoxysilane, 1,1,2,2-tetrafluoroethyltrichlorosilane, pentafluorophenyldimenthylchlorosilane, 2,2,3,3-tetrafluorocyclobutyl, etc.
Moreover, KP 801 (Shinetsu Kagaku, trade name) which is a perfluoroalkylsilicone type water-repellent agent or a photocurable type fluorine type liquid resin, such as DEFENSA (DIC, trade name), etc., which is diluted with Daifuron (DAIKIN KOGYO, trade name), etc. is coated in a thin film on an elastic support such as silicone rubber, etc., and after evaporation of the solvent, the film is transferred onto the recording head surface to form an ink-repellent film.
On the other hand, in an ink jet recording device, water contained in ink or recording medium may be evaporated to make the atmosphere of the recording head highly humid, and depending on the conditions such as the temperatures of the recording head or in the atmosphere, etc., dew formation may sometimes occur on the ink jet ejecting surface.
also, splashed ink from the recording medium. may also wet the ink ejecting surface.
The phenomena such as dew formation, wetting as mentioned above become more conspicuous in the case of using a fixing heater for accelerating fixing of the recorded image onto a recording medium or in the case when the dot duty of the recorded image is high.
Thus, when dew formation or wetting has occurred on the ejecting surface, the ejecting surfaces becomes attached nonuniformly with water droplets, etc., and these attached water droplets will attract nonuniformly the ejected ink when the ink is ejected through eject openings. As a result variances occur in ejecting directions of ink, ejecting rate and also in ink droplet diameters, whereby lowering in recording quality will be brought about. Also, due to wetting of the ejecting surface, paper powder, dust, etc. are readily attached thereon, and these may have adverse influences on the ink ejecting direction of ink, etc., or cause clogging of the eject openings to occur, whereby lowering of recording quality may be caused.
As a measure to cope with such troubles, it has been practiced to remove dew formation, wetting, etc., by wiping the ejecting surface at predetermined timing.
For example, by use of a blade comprising a silicone rubber, etc, as the wiping means, the blade is engaged with the ejecting surface as accompained with the movement of the recording head, thereby wiping off water or dust, etc. of dew formation, wetting, etc.
The fluorosilicone type ink-repellent agent of the prior art, although excellent in the ink-repellent effect, tended to be weaker to the abrasion force from outside accompanied with the wiping actuation. The principal cause for these tendencies resided in use of a substance having a long aliphatic chain as represented by -C.sub.8 F.sub.17, etc.
Also, it has been found that the ink-repellent agent is abraded by a wiper to be markedly deteriorated when printing is performed with the head being maintained at a relatively higher temperature (40.degree. to 50.degree. C.).